(1) Field of the Invention
This invention relates to epidural needle devices, and more particularly to medical devices for introducing a needle and/or catheter into the epidural space of a patient.
(2) Prior Art
Epidural anesthesia is a common medical procedure utilized to deliver drugs or local anesthetics to a patient undergoing a major surgical procedure, obstetrical delivery, or diagnostic/theraputic nerve block. There are several methods of doing this. The most common is the loss-of-resistance technique where a needle with a syringe containing saline and /or air is advanced into the patient's epidural space, which is adjacent to the dural sack. As the needle is advanced, the plunger of the syringe is tapped to give a gentle increase in pressure. Resistance to advancement of the plunger in the syringe is felt by the physician as the needle is advanced through the patient's tissues toward the ligamentum flavum. As the needle passes through the ligamentum flavum and enters the epidural space, a sudden loss of resistance to advancement of the plunger will occur. The saline and air can then be injected with ease into the epidural space as a test, thus indicating the proper location of the needle tip. The advancement of the needle should cease once the epidural space has been entered. Otherwise, the needle may pierce the dural sack.
This loss-of-resistance technique is done in 1-2 mm. advances where the syringe plunger is tapped to check for the loss of resistance. The entry into the epidural space is confirmed by the absence of plunger pressure resistance. The syringe would then be separated from the needle for the "single shot" injection of drugs, or the insertion of a catheter into the epidural space, after which the needle is removed. The catheter insertion permits a continuous infusion of medicaments into the epidural space.
A catheter set for spinal anesthesia is shown in U.S. Pat. No. 4,994,036 to Biscoping et al., which includes the use of a guidewire fed into the epidural space, which fits through the needle device after it has been advanced into the epidural space by the loss-of resistance technique.
A trocar assembly is shown in U.S. Pat. No. 4,654,030 to Moll et al, utilized for puncturing a body cavity for subsequent drainage by a cannula. This assembly utilizes a spring loaded safety shield with a fixed trocar, with no visual or audible indicator arrangement.